Remove: kernel unistd*h files from perf's MANIFEST, not used

No need to copy it to a detached tarball as they aren't used anymore

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-lopmaqi439ke10g1j9cxrxwt@git.kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>